The present invention relates to power tools and, more particularly, to an impacting drive mechanism for a power tool.
A hammer drill is one type of power tool including an impacting drive mechanism or hammer mechanism. Typically, the hammer mechanism includes first and second cam members having mating ratchet surfaces and a spring to bias the cam members and ratchet surfaces out of engagement. An externally applied biasing force is necessary to overcome the spring bias to cause the ratchet surfaces into engagement. Normally, the first cam member is connected to a rotating spindle and is rotated relative to a second cam member rotatably-fixed to the hammer drill housing to provide a ratcheting action. The relative rotation causes the cam member surfaces to slide and cause the second cam member to separate and move axially relative to the first cam member as the external force is overcome. After the apexes of the ratchet surfaces pass one another, the continually applied external biasing force causes the ratchet surfaces to re-engage, providing an impact.
A rotary hammer is another type of power tool including a hammer mechanism. This hammer mechanism typically includes a free floating impacting mass pneumatically driven by a reciprocating piston.